The Role of Money In the McConnell-Bevin Blowout

Mitch McConnell comfortably defeated Matt Bevin this week in the Senate GOP nomination primary in Kentucky. The Associated Press put it in an odd way, however, when they wrote:

Bevin spent $3.3 million in his bid as a political newcomer backed by various tea party groups. McConnell drowned him out with more than $9 million in spending. Outside groups spent millions more defending his conservative credentials.

Sure, Mitch McConnell and groups that supported him may have spent a lot on this primary campaign. But McConnell didn't exactly eke out a close race - he blew Bevin away, winning 60% to 35%.

The best research on the subject continues to show that money doesn't really matter all that much. A study from University of Chicago economist Steve Levitt found:

When a candidate doubled their spending, holding everything else constant, they only got an extra one percent of the popular vote. It’s the same if you cut your spending in half, you only lose one percent of the popular vote. So we’re talking about really large swings in campaign spending with almost trivial changes in the vote.

If this is true, McConnell (and associated groups) would have had to outspend Bevin tenfold to have turned a 50/50 race into the blowout that it is. While the numbers that AP cites are only official campaign spending, Bevin had outside groups like the Senate Conservatives Fund and FreedomWorks on his side as well. It's incredibly unlikely that McConnell's money was the sole key to his victory.